DIY Turbo Discussion greddy on a 1.8? homebrew kit?
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2871 vs 3071

 
Old 01-21-2018, 02:23 PM
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Default 2871 vs 3071

All else equal, what would you expect the spool difference to be between a setup with a 2871 with an A/R of .58 vs a 3071 with an A/R of .50.

I realize that this is a pretty basic question, but I've searched through a ton of build threads and looked at a bunch of dynos and the most info I've seen is that most folks consider the 3071 a bit too big, but that was with a higher A/R. I've seen a lot of folks have good luck with the 2871 and I'm not trying to reinvent the wheel. Miataman has a 3076 and is pretty happy with it, though that spools way slower than both the 2871 and 3071 from what I've seen.

That is all. Thanks in advance.

(In b4 dumb question )
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Old 01-21-2018, 02:43 PM
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Well...what does "A/R" mean? What do the numbers mean?
Tell me now...
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Old 01-21-2018, 02:58 PM
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Buy an EFR.
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Originally Posted by codrus View Post
Basically I've come over to the camp of "If something is a reliability problem on the track, just ask Andrew and do what he says".
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Old 01-21-2018, 03:18 PM
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Originally Posted by Savington View Post
Buy an EFR.
+1
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Old 01-21-2018, 04:03 PM
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Originally Posted by ridethecliche View Post
All else equal, what would you expect the spool difference to be between a setup with a 2871 with an A/R of .58 vs a 3071 with an A/R of .50.

I realize that this is a pretty basic question, but I've searched through a ton of build threads and looked at a bunch of dynos and the most info I've seen is that most folks consider the 3071 a bit too big, but that was with a higher A/R. I've seen a lot of folks have good luck with the 2871 and I'm not trying to reinvent the wheel. Miataman has a 3076 and is pretty happy with it, though that spools way slower than both the 2871 and 3071 from what I've seen.

That is all. Thanks in advance.

(In b4 dumb question )
You should twin scroll 7163 and report back
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Old 01-21-2018, 04:24 PM
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Originally Posted by psyber_0ptix View Post
You should twin scroll 7163 and report back
I wish I had built my own manifold and went twin scroll EFR. That's probably going to be my next power upgrade.
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Old 01-21-2018, 04:25 PM
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You keep asking for validation and everyone is tired
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Old 01-21-2018, 04:25 PM
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Originally Posted by ridethecliche View Post
All else equal, what would you expect the spool difference to be between a setup with a 2871 with an A/R of .58 vs a 3071 with an A/R of .50.

I realize that this is a pretty basic question, but I've searched through a ton of build threads and looked at a bunch of dynos and the most info I've seen is that most folks consider the 3071 a bit too big, but that was with a higher A/R. I've seen a lot of folks have good luck with the 2871 and I'm not trying to reinvent the wheel. Miataman has a 3076 and is pretty happy with it, though that spools way slower than both the 2871 and 3071 from what I've seen.

That is all. Thanks in advance.

(In b4 dumb question )
A few hundred RPMs, probably 500-700 is my guess. I assume you are talking garrett turbos.
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Old 01-21-2018, 06:42 PM
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Originally Posted by patsmx5 View Post
A few hundred RPMs, probably 500-700 is my guess. I assume you are talking garrett turbos.
Yup. That I am. Thanks. That just about made my decision for me. I didn't realize it would be that drastic given the lower A/R. I figured it'd spool a bit faster.

Thanks Pat!
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Old 01-21-2018, 09:25 PM
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Originally Posted by Savington View Post
Buy an EFR.
+2

Seriously OP if you're gonna go with an EFR sized turbo, why don't you get an EFR? They are nearly the same price as the garretts for a vastly superior product
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Old 01-21-2018, 10:07 PM
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The hell are you finding dumbass a/r housings like that for those turbos? The smallest generally accepted housings for those is .64. Source: I own(ed) both.
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Old 01-21-2018, 10:48 PM
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Cheap
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Old 01-21-2018, 10:54 PM
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eBay? Neither of those turbos will get anywhere near their power potential with those A/Rs, so it doesn't really matter. They will both spool like *** and make crappy power to boot.

If you really don't want an EFR then buy a 2863 or a 2867 with a proper T25 housing, or buy an EFR and enjoy the same power with much better spool.
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Originally Posted by codrus View Post
Basically I've come over to the camp of "If something is a reliability problem on the track, just ask Andrew and do what he says".
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Old 01-22-2018, 05:06 AM
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Originally Posted by vteckiller2000 View Post
The hell are you finding dumbass a/r housings like that for those turbos? The smallest generally accepted housings for those is .64. Source: I own(ed) both.
This is exactly what I was thinking and why I asked my question. I only remember A/R's in .64 and .86 for these turbos. Plus, what's a brand new 3071 cost? $900 or more? OP ain't spending that...
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Old 01-22-2018, 07:00 AM
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Originally Posted by thirdgen View Post
This is exactly what I was thinking and why I asked my question. I only remember A/R's in .64 and .86 for these turbos. Plus, what's a brand new 3071 cost? $900 or more? OP ain't spending that...
We're all apparently wondering how he's coming up with oddball ideas and wondering why he's going through the mental gymnastics to try to justify taking an alternative path.
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Old 01-22-2018, 08:14 AM
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It's totally possible that the number for the 3071 is wrong or that it's just the compressor housing A/R, but that's what I was told. Because I am finding some with that when I search.

For the 2871, I was going off the part number and A/R that the seller was reporting.
QIM77319 446179-50329 is the part number.
It led to this CHRA
https://www.atpturbo.com/mm5/merchan...e=CHRA-GT2871R

I'm guessing he might have reported that wrong as well haha. No matter...
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Old 01-22-2018, 08:36 AM
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Originally Posted by ridethecliche View Post
All else equal, what would you expect the spool difference to be between a setup with a 2871 with an A/R of .58 vs a 3071 with an A/R of .50.
why are you asking about the compressor A/R on two vastly different turbos and the effects of spool that might have between the two?!?!?!


go back to school and stop playing with turbos.
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Old 01-22-2018, 09:16 AM
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Originally Posted by Braineack View Post
why are you asking about the compressor A/R on two vastly different turbos and the effects of spool that might have between the two?!?!?!


go back to school and stop playing with turbos.
Wasn't asking about the compressor A/R per se.... I asked for the A/R, but looking at specs online... it looks like that was what was reported to me. /shrug.

But turbo's are fun Scott!
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Old 01-22-2018, 10:15 AM
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Is pawning off all responsibility for lack of knowledge and general silliness onto misinformation and other people a millennial thing? kekeke

Originally Posted by Braineack View Post

go back to school and stop playing with turbos.
eleventy billion times +1

(is there such a number? no worries, I'll just say it was reported to me wrong)
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Old 01-22-2018, 10:17 AM
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Just do everything Pat did. Start at the beginning of his build thread and work your way forward.
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